1. Field of the Invention
The instant invention relates to cellular glass pellets having an ash coating bonded thereto which exhibit superior properties as lightweight aggregate for addition to various inorganic and organic matricies. Such pellets are lightweight and have a closed or open cell structure which renders them particularly useful as lightweight aggregate. Also, the lightweight pellets have particular utility as bulk insulation for hollow building walls and the like.
2. Prior Art
From glass pellets of various types have been made heretofore. Pellets have been made by crushing foam glass slabs to form an open-celled lightweight aggregate. Also, closed-cell pellets have been made by the technique disclosed in Vieli, U.S. Pat. No. 3,321,414. In the Vieli patent a mixture of ground glass and a solution containing an alkali metal silicate and an organic material is fed into a granulating device. The granulated particles or pellets leaving the granulating device have a diameter from about 0.5 to about 2.0 millimeters. The alkali metal silicate is present as a binder and organic material is added as a foaming agent. Granular material coming from the granulating device is fed together with a powdered release agent such as powdered corundum or powdered clay (bentonite) into a kiln whereby the organic material is decomposed, the glass softened and the pellet expanded up to five times its original diameter. Vieli indicates that the pellets tend to agglomerate as they expand.
In an article by C. D. Johnston, The Journal of Testing and Evaluation, Volume 2 No. 5, it is disclosed that crushed glass from bottles and the like were added to a cement mixture containing a certain portion of fly ash. The crushed glass did not significantly affect the density of the resulting concrete, and the addition of fly ash to the concrete only partially solved the problem of alkali attack upon the solid glass particle.
Further development of glass pellets or glass beads is disclosed in U.S. Pat. No. 3,365,315 of Beck wherein glass is cellulated to produce micro balloons, that is, small discrete bubbles of glass wherein the glass is cellular in shape and consists substantially of a single cell.